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Future Direction
Future Coating Methods Corrosion prevention and the environment go hand-in-hand. Researchers at an American company named Cortec Corporation have created the eco-friendly CorShield VpCI Transit Coating, which is a suitable replacement for the commonly used oil-based coatings. CorShield is free of VOCs, and therefore has no impact on air quality and groundwater. It dries to a clear film within 30 minutes of application at ambient temperature.21 Moreover, researchers at Monash University (in Australia) and Rice University (in the U.S.) have developed a graphene coating that is immune to corrosion. Graphene is an ultra thin layer of carbon atoms, which is applied to a metal surface via chemical vapor deposition (CVD).25 CVD uses no solvents, and is efficient over large areas.23 It has only been applied to copper thus far, but the same technique has potential to be utilized for a steel surface. These future environmentally friendly methods of corrosion prevention are conceivable on a large scale, and will ultimately help reduce air and water pollution. 'Smart Coatings' Smart coatings are known for their ability to respond to changes in environmental conditions. This may involve changes in temperature, pH or pressure; and even the presence of radiation or mechanical work. Emerging examples of smart coatings in the last decade have been self-healing coatings. The major component of these coatings used to be chromium (VI), however due to its carcinogenic nature, other alternatives have been developed which include aluminum and magnesium alloys, cerium, sodium tetraoxomolybdate, silica, and fluoro-organic compounds. Effective materials of coatings used to protect steel are polypyrrole and polyalinine. Both materials cause steel passivation against water and oxygen molecules in the atmosphere (or surface). Polypyrrole possesses ion exchange properties such that with the addition of PMo12O403- and HPO42- ions, MoO42- (tetraoxomolybdate) ions form via hydrolysis. Self-healing is achieved when MoO42- reacts with iron, forming a protective coating, and thus preventing corrosion. In another case, polyalinine can work in combination with MoO42- ions to avoid iron dissolution.27 The company American NanoMyte has developed self-healing anticorrosion coatings (as shown above). In their application, the metal-to-be-protected is covered in three layers from top to bottom by a self-healing topcoat, a self-healing primer, and a self-healing pretreatment. When a crack forms in the topcoat and spreads through the layers, the ions of the materials contained in the layers react with the metal, and form the passivation layer, i.e. the protective coating.22 Material Development in Canada In the 2013-2014 Global Competitiveness Report published by the World Economic Forum, Canada was ranked number 12 in terms of infrastructure compared to 147 other countries in the world.26 Despite this impressive ranking, the current cost of repairing infrastructure in Canada, including bridges and other concrete structures is totaled at more than $74 billion.24 Much of this cost is due damage caused by corrosion. Research and development in anti-corrosion technologies, and applying them in the real world, is key to reducing costs in the long-run for the sake of the country’s economy. A research group at Université de Sherbrooke developed fibre-reinforced polymer (FRP) reinforcing bars to replace common steel reinforcing rods in bridges. This material has the potential to quadruple the lifetime of the structure- it may be preserved for 100 years or longer without major repairs. FRP is usually composed of carbon or glass fibers, which are then embedded in a resin mold made of polyester or vinylester. FRP rods look like steel rods, but are remarkably corrosion resistant in “extreme” conditions, at least twice as strong and only one-fifth the weight of conventional bars. FRP material has been tested on bridges throughout Canada, including the Joffre Bridge in Sherbrooke, under real-time traffic and environmental conditions.24 The result of the study concluded with positive performance results, thus the usage of FRP reinforcing bars may hopefully grow across the country.